autoplay - Specifies that the video will start playing as soon as it is ready
controls - Specifies that video controls should be displayed (such as a play/pause button etc).
height (pixels) - Sets the height of the video player
loop - Specifies that the video will start over again, every time it is finished
muted - Specifies that the audio output of the video should be muted
poster - URL Specifies an image to be shown while the video is downloading, or until the user hits the play button
width (pixels) - Sets the width of the video player

What ever @SLiCK_303 suggested is the right thing to do.
Make sure you have email template files for your language.
Inside modules/sendtoafriend/mails/nl
And themes/your_theme/modules/sendtoafriend/mails/nl

You should have 2 files.
send_to_a_friend.html and send_to_a_friend.txt